As Houston's grocery scene becomes increasingly competitive, Kroger, Walmart and H-E-B will again dominate the market this year.

The companies are ranked Nos. 1, 2 and 3, respectively, on this year's Chronicle 100 list of the region's biggest grocers, according to the number of store locations. Each will continue to add stores in the area and compete fiercely with new products and technology. Kroger has 101 locations in the area, Walmart has 100 and H-E-B has 94.

Houston's growth and diversity have fueled the expansion of its grocery market in recent years. Kroger and H-E-B have competed especially aggressively and added dozens of locations across the region.

Joy Partain, regional spokeswoman for Kroger, said the grocer has upped its game by expanding its produce sections and organic products in response to consumer demand. It has also grown its grab-and-go offerings as shoppers seek healthier convenience options.

Kroger further focused convenience last summer when it launched ClickList, its curbside grocery pickup service, in Houston-area stores. The company plans to expand the service to another 30 local stores this year, bringing the total to more than 60.

"Less time doing errands means more time for family," Partain said. "We are catering to demand."

The company opened three new stores so far this year, and it plans to open three more.

Walmart has made similar adjustments to many of its grocery sections by emphasizing produce and organics. It's also piloting new technology, remodeling locations and revamping employee training programs throughout the region as part of a substantial investment in its workers, stores and online operations.

"Retail is evolving, and shoppers' needs today are changing," said Anne Hatfield, regional spokeswoman for Walmart. "Convenience is so important."

The company most recently debuted new features at a store that opened near Tomball earlier this year. The store is one of three nationwide equipped with the company's Scan & Go technology, which enables customers to bypass the standard checkout line by scanning and paying for items with mobile phones or store-supplied devices.

"That is a great example of how Houston is important to us because that store is one of a kind," Hatfield said.

The company most recently opened a Supercenter in Katy, and it plans to open another in Sugar Land this summer.

H-E-B, which competes fiercely on price and selection, will continue to grown in the region this year. Houston president Scott McClelland said it might add as many as 12 stores within the 18 months in areas such as Baytown, Richmond and Katy.

"We're going to have an aggressive store expansion program," he said. "There are large parts of the city that don't have H-E-B stores."

The company is also planning a multilevel store in the Heights, the first of its kind in Houston. And it recently completed a $10 million expansion of its Central Market store on Westheimer, which is piloting new products and services the company might roll out to other locations. At 85,000 square feet, the store is the largest in the Central Market division.

McClelland noted that the Houston grocery market is expected to become even more competitive as the major players continue to expand and smaller ones invest more heavily in the area.

Houston commercial real estate firm Wulfe & Co. expects that Aldi, a European discount grocer, will add 10 locations in the area this year. Lidl, one of its main competitors, has indicated plans to break into the market, and specialty grocers including Whole Foods continue to expand.

"The strategy that got you to success in one year isn't necessarily going to get you there the next year," McClelland said. "The sands shift, and you have to be malleable."